The present invention relates to hydraulic cylinders which are used to operate heavy equipment, such as lifts, cranes, and the like.
In particular, the invention comprises a novel valve having a geometry designed to synchronize the position of two or more hydraulic cylinders operating together at the end of either or both of their directions of stroke.
More particularly, the invention provides an improved valve structure which enables the above-described valve to accomplish its objective, and wherein the valve occupies a very small space.
If two cylinders are operating in parallel, differences in leakage across piston seals, differences in cylinder or rod diameters, or other reasons, can cause differences in cylinder position to accrue over time. The rods and ends of these parallel cylinders are often fixed to the same structures. Should the cylinders become “out of phase” with respect to one another (with one cylinder fully extending or fully retracting before the other), undesirable deformation stresses such as twisting can result if the cylinders are driving the same structure.
An example of the use of parallel hydraulic cylinders, in which the cylinders are attached to the same structure, is a device in which the cylinders are attached to the main boom of a crane.
An example of two cylinders working in parallel, but attached to different structures, is outrigger cylinders. Hydraulic outriggers are often provided on mobile lifts, cranes, and construction equipment to stabilize the vehicle on which the lift, crane, or construction tool (shovel or bucket) is mounted.
Outriggers generally serve two purposes. The first is to eliminate the vehicle suspension, and possibly pneumatic tires, in the support of the crane. Outriggers will generally lift the vehicle tires off of the ground such that the vehicle has a rigid support. It is undesirable for a crane platform or the like to move or bounce.
The second purpose is to widen the vehicle's contact with the ground so that it becomes more difficult to extend the center of gravity of the vehicle over the most lateral contact point with the ground. Such extension of the center of gravity will result in tipping of the vehicle. Using a crane as an example, the wider the contact with the ground, the larger the “load envelope” within which the fully loaded crane can safely operate.
Should outrigger cylinders become out of phase due to accrual of differences in piston leakage, one outrigger will strike the ground before the other, and the result will be tilting of the vehicle, a condition that the outriggers are provided to prevent.
The present invention provides a solution for the problems described above, by providing an improved phaser valve which assists in synchronizing two or more cylinders.